"use client";

import { createContext, useContext, useEffect, useState } from "react";

type Theme = "light" | "dark" | "system";

type ThemeProviderProps = {
  children: React.ReactNode;
  defaultTheme?: Theme;
  storageKey?: string;
};

type ThemeProviderState = {
  theme: Theme;
  setTheme: (theme: Theme) => void;
};

const initialState: ThemeProviderState = {
  theme: "system",
  setTheme: () => null,
};

const ThemeProviderContext = createContext<ThemeProviderState>(initialState);

export function ThemeProvider({
  children,
  defaultTheme = "system",
  storageKey = "theme",
  ...props
}: ThemeProviderProps) {
  const [theme, setTheme] = useState<Theme>(defaultTheme);

  // 在客户端加载时从localStorage获取主题
  useEffect(() => {
    // 确保代码只在客户端执行
    if (typeof window !== "undefined") {
      const storedTheme = localStorage.getItem(storageKey) as Theme;
      if (storedTheme) {
        setTheme(storedTheme);
      }
    }
  }, [storageKey]);

  // 应用主题到HTML根元素
  useEffect(() => {
    // 确保代码只在客户端执行
    if (typeof window !== "undefined") {
      const root = window.document.documentElement;
      root.classList.remove('light', 'dark');
      if (theme === "system") {
        const systemTheme = window.matchMedia("(prefers-color-scheme: dark)")
          .matches
          ? "dark"
          : "light";
        
        root.classList.add(systemTheme);
        return;
      }
      
      root.classList.add(theme);
    }
  }, [theme]);

  const value = {
    theme,
    setTheme: (theme: Theme) => {
      if (typeof window !== "undefined") {
        localStorage.setItem(storageKey, theme);
      }
      setTheme(theme);
    },
  };

  return (
    <ThemeProviderContext.Provider {...props} value={value}>
      {children}
    </ThemeProviderContext.Provider>
  );
}

export const useTheme = () => {
  const context = useContext(ThemeProviderContext);
  
  if (context === undefined)
    throw new Error("useTheme must be used within a ThemeProvider");
  
  return context;
};
